Rotavirus has a diameter close to 1,000 _ with three layers of protein shells and six structural proteins. Ms. A. Shaw, a graduate student of Dr. Prasad, is using our facility to determine the structural variations of the virus with and without proteolytic treatment. She has found that the structural features of the spike proteins depend the procedures used to grow the virus. A significant structural variation seen on the spike protein provides a useful framework for the rotavirologists to interpret the infectivity of the virus in terms of the molecular structure determined by electron cryomicroscopy and image reconstruction.